[Wien] Convergence problem in mbj potential calculation

[Fecher, Gerhard]

Interesting approach
as in Li2NiTiO4 the Li, Ni, and Ti atoms are randomly distributed on the 4a site with oxygen on 4b of the NaCl lattice
therefore one better should write (Li0.5Ti0.25Ni0.25)O 

Ciao
Gerhard

DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:
"I think the problem, to be quite honest with you,
is that you have never actually known what the question is."

====================================
Dr. Gerhard H. Fecher
Institut of Inorganic and Analytical Chemistry
Johannes Gutenberg - University
55099 Mainz
and
Max Planck Institute for Chemical Physics of Solids
01187 Dresden
________________________________________
Von: Wien [wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von shamik chakrabarti [shamikphy at gmail.com]
Gesendet: Mittwoch, 14. Juni 2017 15:39
An: A Mailing list for WIEN2k users
Betreff: Re: [Wien] Convergence problem in mbj potential calculation

Dear Gerhard & Laurence,

                                    Thank you very much for your reply & suggestions. The structure was initially of Li2NiTiO4. The space group is Fm-3m. We have created a 1x1x1 supercell (with target lattice primitive) and then distributed Li, Ni & Ti with 2:1:1 ration at 4b site. 4a site contains oxygen. Then we have optimize the volume and force per atom of the structure sequentially & results in the present structure. The xrd generated by the present structure matches exactly with the experimental xrd of Li2NiTiO4.

However, we have shifted the mixing procedure from PORT to MSR1 and the simulation is converging well now.

with regards,


On Wed, Jun 14, 2017 at 3:17 PM, Laurence Marks <L-marks at northwestern.edu<mailto:L-marks at northwestern.edu>> wrote:
I have said this before, but it is worth repeating: the most common reason a calculation does not converge is because the structure/model is unphysical/unchemical. Your Ti-O bonds are too long, the structure is "obviously" wrong.

Scientific rigor is not optional. What is the R-factor? Are the temperature factors sane? Is there an independent​ measurement of the composition, e.g. ICP? Have you measured that it is FM?

---
Professor Laurence Marks
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On Jun 14, 2017 04:24, "Fecher, Gerhard" <fecher at uni-mainz.de<mailto:fecher at uni-mainz.de>> wrote:
Indeed, your compound is also metallic already with PBE, this you did not tell when I asked about PBE.
Also, the PBE does not result in a ferromagnetic state, I guess ?



--
Professor Laurence Marks
"Research is to see what everybody else has seen, and to think what
nobody else has thought", Albert Szent-Gyorgi
www.numis.northwestern.edu<http://www.numis.northwestern.edu><http://www.numis.northwestern.edu> ; Corrosion in 4D: MURI4D.numis.northwestern.edu<http://MURI4D.numis.northwestern.edu><http://MURI4D.numis.northwestern.edu>
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Dr. Shamik Chakrabarti
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Dept. of Condensed Matter Physics and  Material Science
S N Bose National Centre for Basic Sciences
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--
Dr. Shamik Chakrabarti
Post Doctoral Research Associate
Dept. of Condensed Matter Physics and  Material Science
S N Bose National Centre for Basic Sciences
Kolkata-700098
INDIA